JPH0785434A - Magnetic recording-reproducing device - Google Patents

Abstract

PURPOSE:To prevent magnetization of a head due to a disk-shaped magnet and thereby to enlarge C/N by disposing a head chip at a position at which a phase angle satisfies a prescribed relationship with the central angle of a sectoral part. CONSTITUTION:A head chip 13 is disposed at a position at which a phase angle thetasatisfies the relationship of 0.4alpha<=theta<=0.6alpha. In this expression, alpha denotes the central angle of a sectoral part. By limiting the relationship in disposition between the head chip 13 and a disk-shaped magnet 10 in this way, the strength of a leakage magnetic field from the disk-shaped magnet 10 in the vicinity of the head chip 13 is made smaller than that in the vicinity of a polarity boundary plane. Besides, the direction of the leakage magnetic field of the disk-shaped magnet 10 in the vicinity of a head gap 11 forms a virtually right angle to the direction of a magnetic field generated in the head gap, and therefore the effect of the leakage magnetic field on the head chip 13 is small. As the result, magnetization of a head by the magnet 10 is prevented, an output becomes large consequently and, after all, an C/N ratio becomes excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus having a rotating cylinder.

[0002]

2. Description of the Related Art Conventionally, a video tape recorder (VT
A rotary cylinder is mounted in a magnetic recording / reproducing apparatus for recording / reproducing signals on / from a magnetic tape such as R). A magnetic head for recording / reproducing information on / from a magnetic recording medium is arranged on the rotating cylinder. The magnetic head has a head chip to which the winding is attached. At the time of recording, a magnetic field is generated from the head gap of the head chip by passing a current through the winding. At the time of reproduction, the magnetic field in the head gap of the head chip is changed by the magnetic medium, so that a current flows through the winding.

A motor for rotating the magnetic head is built in the unit of the rotary cylinder. The rotor part of the motor is a disk-shaped multi-pole permanent magnet (hereinafter referred to as "magnet").
Have). This magnet receives a magnetic force from the coil of the stator part of the motor, which produces a force for rotating the rotor part.

A typical conventional positional relationship between the head gap of the head chip and the magnet will be described with reference to FIG. The magnetic head, as shown in FIG.
Has a head chip 13 wound around it. Winding 14
A magnetic field is formed from the head gap 11 of the head chip 13 by passing a current through the head chip 13. The head chip 13 is fixed to the head base 12. Head base 12
Is fixed inside the rotary cylinder 21 by a fixing screw 15. When the rotary cylinder is rotated by the motor, the head gap 11 of the head chip 13 also rotates.

The magnetic head is located above the magnet 10, as shown in FIG. The head chip 13 and the magnet 10 have a fixed positional relationship due to a portion (not shown) of the rotary cylinder, and this relationship does not change even when the motor rotates.

In a typical conventional rotating cylinder,
As shown in FIG. 4, the head gap 11 has the magnet 1
The head chip 13 is arranged so as to be located above the polar boundary portion between the S pole and the N pole of 0. Even when a combination magnetic head in which two head chips 13 are provided on one head base 12 is adopted, the head gap 11 is provided above the polar boundary portion between the S pole and the N pole.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In a small VTR, such as a video movie, the device is becoming more compact. Therefore, the size of the rotary cylinder also necessarily needs to be reduced. When the rotating cylinder is downsized,
The motor magnet 10 for rotating the rotary cylinder approaches the head chip 13. As a result, the leakage magnetic field generated from the magnet 10 is more likely to magnetize the head chip 13 of the magnetic head. When the head chip 13 is magnetized, it has an influence such as a reduction in reproduction output. For example, the magnetized head chip 13 may erase a track recorded on the magnetic tape, and this erase reduces the reproduction output (reduces the signal-to-noise ratio). It is required to reduce the influence of the leakage magnetic field from the motor magnet 10 to a negligible level.

The present invention has been made to solve the above problems, and an object thereof is to provide a magnetic recording / reproducing apparatus in which the influence of a magnetic field from a motor magnet on a head chip is reduced. is there.

[0009]

A magnetic recording / reproducing apparatus according to the present invention comprises a fixed cylinder, a rotary cylinder rotatably supported by the fixed cylinder, and a head chip fixed to the rotary cylinder. In the recording / reproducing apparatus, the rotating cylinder has first fan-shaped parts having a first polarity and second fan-shaped parts having a second polarity opposite to the first polarity arranged alternately. The stationary cylinder has a disk-shaped magnet, the fixed cylinder has a stator coil that applies a magnetic force to the disk-shaped magnet, and thereby rotates the rotating cylinder, and the head chip has a center of the fan-shaped portion. When the angle is α, an imaginary plane including both the center of the head gap of the head chip and the rotation axis of the rotary cylinder, and two polarities sandwiching a fan-shaped portion traversed by the plane. Phase angle while the forms of the field plane theta is sure to meet the relationship of 0.4α ≦ θ ≦ 0.6α, the are arranged on a rotating cylinder, the object is achieved.

A first magnetic shield means arranged between the head chip and the disk-shaped magnet may be further provided.

The first magnetic shield means includes a thin plate made of a magnetic material and having a thickness of 1 mm or less, and the head chip is arranged such that the height of the head chip is 2.9 mm or less. Good.

A second magnetic shield means arranged between the fixed cylinder and the stator coil may be further provided.

The first magnetic shield means and the second magnetic shield means may be made of a high saturation magnetic flux density material.

Another magnetic recording / reproducing apparatus of the present invention comprises a fixed cylinder, a rotating cylinder rotatably supported by the fixed cylinder, and a plurality of head chips fixed to the rotating cylinder. In the device, the rotating cylinder has the disks in which first sectors having a first polarity and second sectors having a second polarity opposite to the first polarity are alternately arranged. -Shaped magnet, the fixed cylinder has a stator coil that applies a magnetic force to the disk-shaped magnet, thereby rotating the rotating cylinder, and at least one head chip of the plurality of head chips. Is a virtual including both the center of the head gap of the at least one head chip and the rotation axis of the rotary cylinder when the central angle of the sector is α. The surface is arranged on the rotating cylinder such that the phase angle θ formed by one of the two polar boundary planes sandwiching the sector crossing the plane satisfies the relation 0.4α ≦ θ ≦ 0.6α. The above object is achieved thereby.

Of the plurality of head chips, the difference in phase angle between the two head chips farthest apart may be 0.2α or more.

The magnetic recording / reproducing apparatus of the present invention is a magnetic recording / reproducing apparatus having a fixed cylinder, a rotating cylinder rotatably supported by the fixed cylinder, and a plurality of head chips fixed to the rotating cylinder. And the rotating cylinder comprises a first sector having a first polarity,
And the disk-shaped magnets in which the second fan-shaped portions having the second polarity opposite to the first polarity are alternately arranged, and the fixed cylinder exerts a magnetic force on the disk-shaped magnets, A stator coil for rotating the rotary cylinder is thereby provided, and at least one head chip among the plurality of head chips has a MIG (metal in g) structure.
ap) a head chip, and the MIG head chip is
When the central angle of the sector is α, a virtual plane including both the center of the head gap of the MIG head chip and the rotation axis of the rotary cylinder, and two polar boundary planes sandwiching the sector traversed by the plane. The phase angle θ formed by one of the two is arranged on the rotary cylinder so as to satisfy the relationship of 0.4α ≦ θ ≦ 0.6α,
Thereby, the above object is achieved.

Among the plurality of head chips, the head chip arranged at a position where the phase angle θ does not satisfy the relationship of 0.4α ≦ θ ≦ 0.6α is a head chip having a non-magnetic substrate. Good.

Among the plurality of head chips, the head chip arranged at a position where the phase angle θ does not satisfy the relationship of 0.4α ≦ θ ≦ 0.6α may be a laminated amorphous head chip.

The depth of the head gap of the MIG (metal in gap) head chip may be 10 μm or less.

[0020]

According to the present invention, the phase angle θ is 0.4α ≦ θ ≦
The head chip is arranged at a position satisfying the relation of 0.6α. Since the positional relationship between the head chip and the disk-shaped magnet is limited in this way, the strength of the leakage magnetic field from the disk-shaped magnet in the vicinity of the head chip becomes smaller than that in the vicinity of the polar boundary plane. Further, since the direction of the stray magnetic field of the disk-shaped magnet near the head gap is substantially perpendicular to the direction of the magnetic field generated in the head gap, the stray magnetic field has less influence on the head chip. As a result, it is possible to prevent the head from being magnetized by the disk-shaped magnet. As a result of preventing the head from magnetizing, the output is increased (the CN ratio is improved).

By disposing a magnetic shield between the head chip and the disk-shaped magnet or between the fixed cylinder and the stator coil, the influence of the leakage magnetic field is further reduced.
By configuring this magnetic shield with a high saturation magnetic flux density material, it is possible to greatly suppress the influence of the leakage magnetic field with a small magnetic shield. For example, the thickness of the magnetic shield means is 1 mm or less, and the height of the head chip is 2.9 mm.
With the following, the axial thickness of the cylinder can be reduced, and the magnetic recording / reproducing apparatus can be downsized.

In the case of having a plurality of head chips, only the head chips which are desired to avoid the influence of the leakage magnetic field are arranged at the positions satisfying the above relationship. As a result, the strength of the leakage magnetic field from the disk-shaped magnet becomes smaller than that in the vicinity of the polar boundary plane, and the direction of the leakage magnetic field of the disk-shaped magnet in the vicinity of the head gap is almost the same as the direction of the magnetic field generated in the head gap. Due to the right angle, the effect of stray magnetic fields can be avoided.

Of the plurality of head chips, when the difference between the phase angles of the two head chips that are farthest apart is 0.2α or more, only the head chip which is desired to avoid the influence of the leakage magnetic field is positioned to satisfy the above relationship. If the other heads are arranged, there is no restriction in the arrangement of the other heads, which helps miniaturize the rotary cylinder.

Among the plurality of head chips, the MIG head chip is arranged at a position satisfying the above relationship. As a result, the influence of the leakage magnetic field can be suppressed. Further MI
The G head chip is a material having a high saturation magnetic flux density,
And the shape of the core is made to concentrate the magnetic flux (the width of the core is the smallest in the gap part)
Therefore, a large output can be obtained.

Of the plurality of head chips, a head chip having a non-magnetic substrate may be used as the head chip arranged at a position that does not satisfy the above relationship. A head chip (for example, a laminated amorphous head chip) having a non-magnetic substrate is M
Compared with the IG head, the saturation magnetic flux density of the material is small,
Moreover, since the core shape does not concentrate the magnetic flux, the influence of the leakage magnetic field can be reduced.

By setting the depth of the gap of the MIG head to 10 μm or less, the gap area is reduced, so that the magnetic flux is concentrated in the gap portion, and as a result, a large output can be taken out.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic recording / reproducing apparatus according to the present invention will be described below with reference to the drawings.

FIG. 3 shows an outer shape of a rotary cylinder of the magnetic recording / reproducing apparatus according to the present invention, and FIG. 2 is a sectional view of a rotary cylinder unit of the magnetic recording / reproducing apparatus for recording / reproducing a magnetic tape as a recording medium. is there. The outline of the configuration shown in FIGS. 2 and 3 is similar to that of the conventional rotary cylinder.

First, referring to FIG. A head chip 13, which is a part of a magnetic head, is provided on the rotary cylinder 21 of the magnetic recording / reproducing apparatus of this embodiment. Below the rotary cylinder 21, a rotor unit 31 of a motor for rotating the entire magnetic head including the head chip 13 is provided. The head chip 13 is the rotary cylinder 2
1 through the window 34. A PG magnet 32 is provided on the outer circumference of the rotor unit 31. The magnetic field formed by the PG magnet 32 changes as the rotor unit 31 rotates. Rotational phase detection (PG) is executed by detecting this change with the magnetoresistive element 33.

Next, referring to FIG. In the magnetic recording / reproducing apparatus of the present embodiment, the rotating cylinder unit has a fixed cylinder 24 having an outer peripheral surface for guiding the magnetic tape, and a magnetic recording / reproducing on the magnetic tape from the fixed cylinder 24 via the rotating shaft 26 and the bearing 28. The rotary cylinder 21 is provided for supporting the head chip 13 which is a part of the head.

The cylinder unit further comprises a stator coil 25 for driving the rotary cylinder 21 fixed inside the fixed cylinder 24, and a multi-pole magnet 10 magnetized so as to have alternating polarities. A disk-shaped magnet 10 rotating relative to the stator coil 25;
An upper shield plate 23 that covers the upper surface and is made of a high saturation magnetic flux density material
And a lower shield plate 29 made of a high saturation magnetic flux density material provided between the stator coil 25 and the fixed cylinder 24.
It is equipped with.

In the present embodiment, a gap 30 (hereinafter, referred to as a space between the surface of the head base 12 on which the head chip 13 is arranged and the surface of the upper shield plate 23 on which the head chip 13 is arranged) "Head chip height")
It is 1.9 mm. The height 30 of the head chip is set to 3.4 mm or more in the conventional VTR. Further, the thickness of the upper shield plate 23 in this embodiment is 0.5 mm, and the thickness of the lower shield plate 29 is 0.5 mm.
The materials of the shield plates 23 and 29 include Fe and Co.

Next, the positional relationship between the head gap 11 of the head chip 13 and the magnet 10 will be described with reference to FIG. The magnetic head has a head chip 13 on which a winding 14 is wound, as shown in FIG. A head gap 11 is provided in the head chip 13. At the time of recording, by passing an electric current through the winding 14,
A magnetic field is formed from the head gap 11 of the head chip 13. During reproduction, the magnetic field in the head gap 11 changes, so that a current flows through the winding 14. In the present specification, the term “magnetic head” includes a head chip 13 having a head gap 11 and a winding 14, and a head base 12 to which the head chip 13 is fixed. A magnetic head having two head chips may be called a "combination magnetic head", and a magnetic head having three head chips may be called a "multi-magnetic head". The head base 12 is fixed to the rotary cylinder 21 with a fixing screw 15. When the rotary cylinder 21 is rotated by the motor, the head gap 11 of the magnetic head also rotates.

Each magnetic pole of the disk-shaped magnet 10 has an S
It is divided by an imaginary plane (hereinafter, referred to as “polar boundary plane”) that passes through the boundary portion between the pole and the N pole and is perpendicular to the upper surface of the magnet 10. The magnet 10 of the present embodiment is an 8-pole type, and the central angle α of the fan-shaped portion (corresponding to a single magnetic pole, hereinafter referred to as the “fan-shaped portion of the magnet 10”) sandwiched between the adjacent polar boundary planes 16a to 16h is Both are 45 °.

As shown in FIG. 1, the head gap 11
Are arranged at positions not crossing the polar boundary planes 16a to 16h. FIG. 1 also shows two auxiliary lines 18 connecting both ends of the head chip 13 and the center 17 of the rotary shaft 26 of the rotary cylinder 21. In this figure, not only the head gap 11 but also both ends of the head chip 13 do not cross the polar boundary planes 16a to 16h. In other words,
The auxiliary line 18 is located between the two polar boundary planes 16 a and 16 b closest to the head gap 11.

A DC erasing characteristic is used to measure the influence of the leakage magnetic field due to the magnet 10 inside the rotary cylinder 21.
The DC erasing characteristic is a characteristic indicating how much a track on the tape is erased by magnetizing the head chip 13. Specifically, it is measured by the CN ratio. CN representing a DC erasing characteristic when the positional relationship of the head chip 13 with respect to the polar boundary plane 16a is changed.
We investigated how the ratio changes.

First, the above characteristics will be described for a magnetic recording / reproducing apparatus equipped with a "single magnetic head" in which one head chip 13 is arranged on one head base 12. Here, the phase angle θ is introduced as a value that specifies the positional relationship between the head gap 11 and the magnet 10 (see FIG. 1). In the present specification, the “phase angle θ” means
A virtual plane 19 including both the center of the head gap 11 of the head chip and the rotation axis 26 of the rotation cylinder 21.
And the one of the two polar boundary planes 16a and 16b sandwiching a fan-shaped portion across which the virtual plane 19 crosses. As "one of the two polar boundary planes 16a and 16b", one in which the phase angle θ increases when the head gap 11 rotates counterclockwise with respect to the magnet 10 (polar boundary plane 16a) is selected. Head gap 1
In the state where 1 is arranged so as to cross the polar boundary plane 16a (see FIG. 4), the phase angle θ = 0 °.

The experimental conditions are as follows (1) to (5). (1) The CN ratio was measured by changing the position of the head chip in the range of phase angle = 0 ° to 40 °.

(2) In the CN ratio, C (carrier wave) is 2
A single carrier wave of 0.9 MHz (recording wavelength 0.49 μm), N (noise) is 18.6 MHz and 23.3 M
It is the average value of total noise in Hz. C below
The same CN ratio is used for the N ratio.

(3) As the head chip 13, MIG (metal
in gap) head chip was used. The core of the MIG head chip is made of ferrite. This MIG
Since the head has a higher saturation magnetic flux density than a ferrite head, a large output can be obtained. Further, since the head core width is narrowed in the head gap portion so as to concentrate the magnetic flux, this also makes it possible to obtain a large output. However, since the magnetic flux is concentrated, it has the drawback that it is easily affected by the external magnetic field. The core width of the MIG head chip in the gap portion is 60 μm.

(4) The recording medium has a coercive force of 1500
A vapor-deposited tape of Oe (usually called ME tape) was used.

(5) As the magnetic recording / reproducing apparatus, a commercially available domestic VTR (VHS deck) is modified. The cylinder unit is a digital VTR cylinder unit having a cylinder diameter of 21.7 mm.

The graph of FIG. 5 shows the change of the CN ratio when the phase angle θ is changed (when the positional relationship between the head chip 13 and the magnet 10 is changed).

When there is no influence of the leakage magnetic field, the CN ratio is 53 dB. Therefore, the amount of output reduction due to the leakage magnetic field is obtained by the difference from 53 dB. For example, the CN ratio obtained by the head chip 13 arranged at the position of the phase angle = 0 ° is 44 dB. This value is 9 compared with the CN ratio of 53 dB when there is no influence of the leakage magnetic field.
It is a low value by dB. That is, this 9 dB is due to the output reduction due to the leakage magnetic field.

The CN ratio when the phase angle θ = 6 ° is 48d.
B. This is about 5 dB lower than when there is no influence of the stray magnetic field. However, in this value, the CN ratio is improved by about 4 dB as compared with the case where the phase angle θ = 0 °. From this, in the vicinity of the phase angle θ = 0 °, the increase of the phase angle θ tends to prevent the decrease of the CN ratio (that is, the decrease of the output).

From the graph of FIG. 5, it can be seen that when the phase angle θ is 18 ° or more, the CN ratio becomes 53 dB (a value not affected by the leakage magnetic field). Also, it can be seen that the CN ratio does not decrease until the phase angle θ reaches 27 °. Conversely, the phase angle θ
When the angle exceeds 27 °, the CN ratio decreases.

From the above, in the region where the output is not reduced by the leakage magnetic field, the deviation from the center line of the fan 10 of the magnet 10 (the position of the phase angle θ = 22.5 °) is the center angle α of the fan. It can be said that the range is within 10% (± 4.5 °). In other words, the phase angle θ that prevents the head chip from deteriorating the CN ratio due to the leakage magnetic field.
The condition (hereinafter, referred to as “condition not affected by leakage magnetic field”) is 0.5α−0.1α ≦ phase angle θ ≦ 0.5α + 0.1α, that is, 0.4α ≦ phase angle θ ≦ 0.6α. Equation 1) Here, α is the central angle of the fan-shaped portion of the magnet 10 (α = 45 ° when the magnet 10 has 8 poles).

Within the above range, the influence of the leakage magnetic field is small for two main reasons.

In the vicinity of the center line (phase angle θ = 0.5α) of each sector of the magnet 10, the polar boundary planes 16a ...
The magnetic field strength itself is smaller than that in the vicinity of 16 h.

The direction of the magnetic field generated by the magnet 10 near the center line of each sector of the magnet 10 is substantially perpendicular to the direction of the magnetic field generated in the head gap 11 during recording and reproduction.
The distribution of the magnetic field generated from the magnet 10 repeats a symmetrical distribution with respect to each sector. Therefore, as shown in FIG. 5, the graph in the case where the fan-shaped portion of the magnet 10 has the S pole (solid line) and the graph in the case where the fan-shaped portion has the N pole (dotted line) substantially match. From the graph of FIG. 5, it is understood that the phase angle is preferably 0.5α−0.05α ≦ θ ≦ 0.5α + 0.05α.

When a 16-pole magnet is used as the magnet 10, the central angle α of the fan-shaped portion is 22.5 °. This α
The above "conditions not affected by leakage magnetic field" (0.5α-
0.1α ≤ phase angle θ ≤ 0.5α + 0.1α),
In the case of a 16-pole magnet, the range not affected by the leakage magnetic field (specifically, 22.5 ° -2.25 ° ≦ phase angle θ ≦ 2
2.5 ° + 2.25 °) is required. In the case of 32 magnetic poles, 11.25 ° -1.125 ° ≦
If the head gap is arranged in the region within the phase angle θ ≦ 11.25 ° + 1.125 °, it is not affected by the leakage magnetic field.

Next, the influence of the leakage magnetic field on the output (CN ratio) when the above-mentioned "head chip height" was changed was examined. The graph of FIG. 6 shows the CN ratio when the height 30 of the head chip changes when the phase angle θ = 0 °. As shown in the graph of FIG. 6, when the height 30 of the head chip is set to 1.9 mm, the CN ratio is 44 dB, which is 9 dB lower than the reference value of 53 dB. If the height of the head chip is made smaller than this to 1.7 mm, the CN ratio becomes 4
It is 0 dB, which is 13 d more than the reference value of 53 dB.
B is low. At 2.9 mm with the height of the head chip increased, it becomes 52 dB, and the CN ratio is 1 dB from the reference value of 53 dB.
Only low. Further, when the height of the head chip is increased to 3.4 mm, the CN ratio becomes 53 dB, and the CN ratio does not decrease.

Next, the graph of FIG. 7 shows that the phase angle θ = 0.
5α = 22.5 ° (However, the central angle of the fan-shaped part α = 45 °)
In this case, the CN ratio is shown when the height 30 of the head chip changes. As shown in the graph of FIG. 7, when the phase angle θ is set to 22.5 °, the CN ratio becomes 53 dB, which is the reference value, in the region where the head chip height 30 is 1.7 mm to 3.4 mm. Compared to the decline. From this, the head chip 13 and the magnet 1
If the phase angle θ is equal to 0.5α even if the head chip height 30 is 2.9 mm or less, CN
It is possible to prevent the ratio from decreasing.

As described above, when the phase angle θ is 0.4α ≦ θ ≦ 0.6α and the height of the head chip is 2.9 mm or less, with the central angle of the fan-shaped portion of the magnet 10 being α, the influence of the leakage magnetic field is exerted. I do not receive it. If the phase angle θ is 0.4α ≦ θ ≦ 0.6α, the height of the head chip may be 1.7 mm or less, of course.

When the thickness of the upper shield plate 23 is smaller than 0.5 mm, the influence of the stray magnetic field is likely to occur. Therefore, by using the present invention, the influence of the stray magnetic field can be effectively prevented.

Next, the head chip gap depth (gap
The relationship between the depth: GD) and the leakage magnetic field was investigated. The head chip used in the experiment had a gap depth of 10 μm. Gap depths of 20 μm, 10 μm, and 5 μm
8 shows the CN ratio when the MIG head chip that is
Shown in. Here, the CN ratio when not affected by the leakage magnetic field is 0 dB. It was found for the first time by experiments that the smaller the gap depth, the more susceptible it is to the stray magnetic field.
This is because, as described above, the magnetic flux concentrates in the gap portion because the gap width is small (the gap area is small).

On the other hand, the gap of the head chip is
It was found that the CN ratio does not decrease regardless of the depth of the gap if the phase angle θ exists within the range of 0.4α ≦ θ ≦ 0.6α (where α is the central angle of the fan-shaped portion of the magnet 10). . This is because when the head chip is arranged within this range, the head chip is not affected by the leakage magnetic field and is not magnetized. Generally, the smaller the head chip gap depth, the higher the reproduction efficiency and the higher the output signal level. Therefore, in a magnetic recording / reproducing apparatus such as a digital VTR, when the wavelength of a recording signal is as small as about 0.5 μm, the gap depth of the head chip is usually about 10 μm. Especially, the head chip gap depth is 10 μm
In the case of a head chip that is easily affected by the following leakage magnetic field, the phase angle θ is 0.4α ≦ θ
Arranging within the range of ≦ 0.6α is an effective method for making it less susceptible to the leakage magnetic field and preventing the CN ratio from decreasing.

In the above example, the head chip is the MIG head chip, but other head chips (V
For example, a laminated amorphous head chip used in TR may be used. For example, as a typical laminated amorphous head chip, the amorphous portion is Co-Nb.
It consists -ta-Zr, the substrate sandwiching it, there is a head chip composed of a NiO-Ti0 ₂ -MgO of non-magnetic material. The head core width including the width of the substrate is 60 μm, and this core width is the same as that of the MIG head chip.

The following experiment was conducted in order to examine the influence of the stray magnetic field on the head chip. In this experiment, the head chip used in the first experiment was replaced with the laminated amorphous head chip from the MIG head chip. The result is shown in FIG. From this result, when the height of the head chip is 1.9 mm and the phase angle θ is 0 °, the CN ratio decreases by 0.5 dB. This decrease is not so remarkable as the decrease in the CN ratio in the MIG head chip. It was found that the laminated amorphous head chip is less susceptible to the above-mentioned leakage magnetic field than the MIG head chip. This can be explained as follows.

The laminated amorphous head chip has a structure in which amorphous of a magnetic material layer is laminated in a plate shape on a non-magnetic substrate, and the non-magnetic substrate is sandwiched therebetween. The head core width of the laminated amorphous head chip is
Small compared to MIG head chips. It is a non-magnetic substrate that sandwiches the stacked flat plates. Therefore, the amount of magnetization of the head chip due to the leakage magnetic field from the magnet 10 is reduced.

For the laminated amorphous head chip,
Most of the MIG head chips are made of a material having a high saturation magnetic flux density, such as Fe system. The shape of the head core is also such that the magnetic field can be concentrated in the gap to obtain a large output. Therefore, when a magnetic field is generated in the vicinity of the core of the head chip, the magnetic field is likely to concentrate in the head gap (the head chip is easily magnetized), resulting in a decrease in output.

In the above embodiments, the MIG head chip and the laminated amorphous head chip are given as examples. However, the present invention can be applied to other head chips in practice.

An embodiment of the present invention in a magnetic recording / reproducing apparatus having a plurality of head chips will be described with reference to FIG. In order to prevent all of the plurality of head chips from being affected by the leakage magnetic field from the magnet 10, ideally, all of the head chips should be arranged at positions that satisfy the above conditional expression 1. However, in practice, it is often difficult to arrange all the head chips at positions that satisfy the conditional expression 1 described above. The reasons are as follows.

In the case of a VTR for business use, a plurality of head chips are often mounted on one head base or the like. On the other hand, with the miniaturization of equipment, the diameter of the rotating cylinder is becoming smaller and smaller. However, the size of the head chips themselves and the distance between the head chips are not as small as those of the rotary cylinder. Therefore, it is not always easy to dispose all of the plurality of head chips at positions that are less susceptible to the above-mentioned leakage magnetic field. In particular, when the difference in phase angle between the two head chips that are farthest apart from each other among the plurality of head chips is 0.2α (where α is the central angle of the fan-shaped portion of the magnet) or more, all the head chips must meet the conditions. Equation 1 is not satisfied.

In FIG. 10, a plurality of head chips are arranged on the rotary cylinder. Here, three head chips 41, 42 and 43 are attached to one head base 12. For the above-mentioned reason, when it is not possible to arrange all the head chips at positions that are not affected by the leakage magnetic field, the head chips 41 and 42 that are easily affected by the leakage magnetic field, such as the MIG head chip, are set by the conditional expression. It is preferentially placed at a position where 1 is satisfied. On the other hand, the head chip 43 such as a non-MIG system head chip that is not easily affected by the leakage magnetic field may be arranged outside the region that satisfies the conditional expression 1. The non-MIG type head chip includes the above-mentioned laminated amorphous head chip and the like.

By arranging as described above, the degree of freedom in arranging the head chip on the miniaturized cylinder can be increased while avoiding the influence of the leakage magnetic field.

In the above embodiments, a vapor deposition tape is used as the recording medium. As the recording medium, other than this, a Co-based iron oxide tape, a metal-coated tape (MP tape), a CoCr tape, or the like having a coercive force different from that of the vapor deposition tape can be used.

[0068]

According to the present invention, the phase angle θ is 0.4α.
By arranging the head chip at a position satisfying the relation of ≦ θ ≦ 0.6α, it is possible to prevent the head from being magnetized by the disc magnet. As a result of preventing the head from magnetizing, the output is increased (the CN ratio is improved).

By disposing a magnetic shield between the head chip and the disk-shaped magnet or between the fixed cylinder and the stator coil, the influence of the leakage magnetic field is further reduced.
By configuring this magnetic shield with a high saturation magnetic flux density material, it is possible to greatly suppress the influence of the leakage magnetic field with a small magnetic shield. For example, the thickness of the magnetic shield means is 1 mm or less, and the height of the head chip is 2.9 mm.
With the following, the cylinder can be made thin and the magnetic recording / reproducing apparatus can be miniaturized.

In the case of having a plurality of head chips, if only the head chips desired to avoid the influence of the leakage magnetic field are arranged at the positions satisfying the above relationship, the influence of the leakage magnetic field can be effectively avoided.

Of the plurality of head chips, when the difference in phase angle between the two head chips farthest apart is 0.2α or more, only the head chip which is desired to avoid the influence of the stray magnetic field is positioned to satisfy the above relationship. By arranging in, it is possible to effectively avoid the influence of the leakage magnetic field.

By arranging the MIG head chip among the plurality of head chips at a position satisfying the above relationship, a large output can be obtained while suppressing the influence of the leakage magnetic field.

Among the plurality of head chips, as a head chip arranged at a position that does not satisfy the above relationship, a head covering a magnetic layer of the head chip with a non-magnetic substrate or a laminated amorphous head chip is used. The influence of the leakage magnetic field can be reduced.

The gap depth of the MIG head is set to 10
The output can be increased by setting the thickness to μm or less.

[Brief description of drawings]

FIG. 1 is a plan view showing a positional relationship between a head gap of a head chip and a magnet in an embodiment of the present invention.

FIG. 2 is a sectional view showing a rotary cylinder unit of a magnetic recording / reproducing apparatus.

FIG. 3 is a diagram showing an outer appearance of a rotary cylinder unit of the magnetic recording / reproducing apparatus.

FIG. 4 is a plan view showing a positional relationship between a head gap of a head chip and a magnet in a conventional example.

FIG. 5 is a diagram showing changes in the CN ratio when the phase angle θ is changed.

FIG. 6 is a diagram showing changes in the CN ratio when the height of the head chip is changed when the phase angle θ = 0 °.

FIG. 7 shows the case where the phase angle θ = 0.5α = 22.5 °,
The figure which shows the change of CN ratio when changing the height of the head chip

FIG. 8 shows a gap depth (GD) of 20 μm, 10 μm,
And a graph showing changes in the CN ratio when the phase angle θ is changed in the case of 5 μm

FIG. 9 is a graph showing changes in the CN ratio when the phase angle θ is changed when the head chips are MIG head chips and laminated amorphous head chips.

FIG. 10 is a plan view showing a positional relationship between a head gap of a head chip and a magnet in a magnetic recording / reproducing apparatus having a plurality of head chips according to the present invention.

[Explanation of symbols]

10 Magnet 11 Head Gap 12 Head Base 13 Head Chip 14 Winding 15 Fixing Screw 16a, 16b, 16c, 16d, 16e, 16f, 1
6g, 16h Polar boundary plane 17 Center of rotation axis 18 Auxiliary line 19 Virtual plane including both head gap and rotation axis 21 Rotation cylinder 23 Upper shield plate 24 Fixed cylinder 25 Stator coil 26 Rotation axis 28 Bearing 29 Lower shield plate 30 Height of Head Chip 31 Rotor Unit 32 PG Magnet 33 Magnetoresistive Element 34 Cylinder Window 41 Head Chip 42 Head Chip 43 Head Chip

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Kantake 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (11)

[Claims] 1. A magnetic recording / reproducing apparatus having a fixed cylinder, a rotating cylinder rotatably supported by the fixed cylinder, and a head chip fixed to the rotating cylinder, wherein the rotating cylinder comprises a first cylinder. A first sector having a polarity and a second sector having a second polarity opposite to the first polarity having the disc magnets alternately arranged, and the fixed cylinder , Exerts a magnetic force on the disc magnet,
The head chip has a stator coil for rotating the rotary cylinder, and the head chip has both a center of a head gap of the head chip and a rotary shaft of the rotary cylinder when the central angle of the fan-shaped portion is α. The rotating cylinder is configured such that a phase angle θ formed by an imaginary plane that includes it and one of two polar boundary planes that sandwich a fan-shaped portion that the plane intersects satisfies a relationship of 0.4α ≦ θ ≦ 0.6α. A magnetic recording / reproducing device disposed on the above. 2. A first magnetic shield means arranged between the head chip and the disk-shaped magnet.
The magnetic recording / reproducing apparatus according to. 3. The first magnetic shield means includes a thin plate made of a magnetic material and having a thickness of 1 mm or less, and the head chip is arranged such that the height of the head chip is 2.9 mm or less. Item 2. The magnetic recording / reproducing apparatus according to item 2. 4. The magnetic recording / reproducing apparatus according to claim 2, further comprising a second magnetic shield means arranged between the fixed cylinder and the stator coil. 5. The magnetic recording / reproducing apparatus according to claim 4, wherein the first magnetic shield means and the second magnetic shield means are made of a high saturation magnetic flux density material. 6. A magnetic recording / reproducing apparatus having a fixed cylinder, a rotating cylinder rotatably supported by the fixed cylinder, and a plurality of head chips fixed to the rotating cylinder, wherein the rotating cylinder comprises: A first sector having a first polarity, and a second sector having a second polarity opposite the first polarity, the disc-shaped magnets being alternately arranged, The fixed cylinder exerts a magnetic force on the disc-shaped magnet,
A head coil of the at least one head chip is provided when at least one head chip of the plurality of head chips has a central angle α of the fan-shaped portion. The phase angle θ formed by an imaginary plane including both the center of and the rotation axis of the rotary cylinder and one of the two polar boundary planes sandwiching the fan-shaped portion traversed by the plane is 0.
A magnetic recording / reproducing apparatus arranged on the rotating cylinder so as to satisfy the relationship of 4α ≦ θ ≦ 0.6α. 7. The magnetic recording / reproducing apparatus according to claim 6, wherein the difference in phase angle between the two head chips that are farthest apart from each other is 0.2α or more. 8. A magnetic recording / reproducing apparatus, comprising: a fixed cylinder; a rotating cylinder rotatably supported by the fixed cylinder; and a plurality of head chips fixed to the rotating cylinder. A first sector having a first polarity, and a second sector having a second polarity opposite the first polarity, the disc-shaped magnets being alternately arranged, The fixed cylinder exerts a magnetic force on the disc-shaped magnet,
And a stator coil for rotating the rotary cylinder, wherein at least one head chip of the plurality of head chips is a MIG (metal in gap) head chip, and the MIG head chip is the fan-shaped portion. And a central angle of α is α, a virtual plane including both the center of the head gap of the MIG head chip and the rotation axis of the rotary cylinder,
The phase angle θ formed by one of the two polar boundary planes sandwiching the sector crossing the plane is 0.4α ≦ θ ≦
A magnetic recording / reproducing device arranged on the rotating cylinder so as to satisfy the relationship of 0.6α. 9. A head chip having a substrate made of a non-magnetic material, of the plurality of head chips, the head chip arranged at a position where the phase angle θ does not satisfy the relationship of 0.4α ≦ θ ≦ 0.6α. The magnetic recording / reproducing apparatus according to claim 8, which is a chip. 10. A phase angle θ of a plurality of head chips.
9. The magnetic recording / reproducing apparatus according to claim 8, wherein the head chip arranged at a position that does not satisfy the relationship of 0.4α ≦ θ ≦ 0.6α is a laminated amorphous head chip. 11. The magnetic recording / reproducing apparatus according to claim 8, wherein the depth of the head gap of the MIG (metal in gap) head chip is 10 μm or less.